1. Field of the Invention
This invention relates to apparatus for feeding stock material from a coil to a punch press in timed relation with the punching operation and more particularly to apparatus for continuously advancing the stock material from a coil and intermittently feeding a preselected length of the stock material to the punch press in timed relation with the punching operation.
2. Description of the Prior Art
It is the conventional practice in high speed automatic press operations to feed a strip of material from a coil to the dies of the press for punching, stamping, cutting or the like of a preselected length of the material. The material must be fed from the coil in timed relation with the punching operation so that when the dies contact the material, the material is released from the feed so that the feed is interrupted and the material is stationarily positioned between the dies. After the punching operation is completed the feed is actuated to advance another preselected length of the material to the press. Therefore, the feeding of the stock material to the press must be coordinated with each punching operation so that prior to each operation a new segment of the material is in position relative to the dies for punching.
U.S. Pat. No. 3,483,782 illustrates and describes a self-contained feed roll for power punch presses. A feed roll is drivingly connected to the punch press crankshaft. An index drive receives the continuous rotation of the crankshaft and converts it to non-continuous, incremental movement of the index drive output shaft which is drivingly connected to the feed roll. With this arrangement the feed roll is not rotated during the pressing portion of the punch press operating cycle. After the punching portion of the operating cycle, the feed roll is rotated to advance another preselected length of stock material to the press dies. The feeding portion of the operating cycle is complete prior to the punching portion.
The following United States Patents relate to material punching and cutting apparatus in which stock material is unreeled from a coil and strips of a preselected length are severed from the unreeled material: U.S. Pat. Nos. 2,272,215; 2,314,367; 2,480,781; 3,053,129; 3,102,673; 3,143,938; 3,244,045; 3,515,553; 3,768,349 and 3,978,703. The principal factor in feeding the stock material to the punch press is coordinating the feeding operation with the punching operation. It is known to provide separate drive for the feed mechanism and the punch press. This, however, creates considerable difficulty in maintaining a timed relation between the feeding operation and the punching operation. Adjustments are generally required by an expert technician to maintain the feeding operation coordinated with the punching operation.
To overcome the problems with providing separate drives for the feed mechanism and the punch press, the feed mechanism is drivingly connected to the punch press. However, because feeding of the stock material to the punch press is intermittent it is not possible without some accommodation to continuously unreel the stock material. Additionally, it was the conventional practice to provide separate drive means for continuously unreeling the stock material from the coil and for intermittently feeding the stock material to the punch press. U.S. Pat. Nos. 2,314,367; 2,272,215; 2,480,781 and 3,053,129 disclose a single drive motor to provide both continuous unreeling from a coil and intermittent feeding to a punch press. To accommodate the periodic interruption of the material feeding, a loop is formed for storing the excess material during the punching operation. Thereafter the material is then fed from the loop to the punch press for subsequent punching. However, unless the same length of material is fed after each punching operation, the resultant product will deviate from the desired configuration.
There is need for an apparatus to control the feeding of stock material to an automatic punch press in which a common power source is provided for continuously unreeling the stock material from a coil and intermittently feeding the stock material to the punch press in timed relation with the punching operation. While it has been suggested by the prior art devices to provide a single drive for continuously unreeling the stock material and intermittently feeding the stock material to a punch press, the prior art devices do not provide means for insuring that the same length of material is fed to the punch press for each cycle of operation.